Chapter 2
General System and Facility Guidelines
Environmental Factors
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An air distribution system should be zoned to deliver an adequate amount of supply air to the cooling air
intake vents of the computer system equipment cabinets. Supply air temperature should be maintained
within the following parameters:
•
Ceiling supply system—From 55° F (12.8° C) to 60° F (15.6° C)
•
Floor supply system—The recommended air intake temperature for the blade server is between 68° F and
77° F (20° C and 25° C) at 90 cfm. Temperatures colder than the minimum may cause false errors.
NOTE
If a ceiling plenum return air system or a ducted ceiling return air system is used, the return
air grill(s) in the ceiling should be above the exhaust area or the exhaust row.
The following three types of air distribution system are listed in order of recommendation:
•
Underfloor air distribution system—Downflow air conditioning equipment located on the raised floor of
the computer room uses the cavity beneath the raised floor as plenum for the supply air. Return air from
an underfloor air distribution system can be ducted return air (DRA) above the ceiling. Perforated floor
panels (available from the raised floor manufacturer) should be located around the front of the system
cabinets. Supply air emitted though the perforated floor panels is then available near the cooling air
intake vents of the computer system cabinets.
•
Ceiling plenum air distribution system—Supply air is ducted into the ceiling plenum from upflow air
conditioning equipment located in the computer room or from an air-handling unit (remote). The ceiling
construction should resist air leakage. Place perforated ceiling panels (with down discharge air flow
characteristics) around the front of the system cabinets. The supply air emitted downward from the
perforated ceiling panels is then available near the cooling air intake vents of the computer system
cabinets. Return air should be ducted back to the air-conditioning equipment through the return air duct
above the ceiling.
•
Above ceiling ducted air distribution system—Supply air is ducted into a ceiling diffuser system from
upflow air conditioning equipment located in the computer room or from an air-handling unit (remote).
Return air from an above ceiling ducted air distribution system may be ducted return air (DRA) above the
ceiling, or ceiling plenum return air (CPRA). Adjust the supply air diffuser system grilles to direct the
cooling air downward around the front of the computer system cabinets. The supply air is then available
near the cooling air intake vents of the computer system cabinets.
Air Conditioning System Installation
All air conditioning equipment, materials, and installation must comply with any applicable construction
codes. Installation of the various components of the air conditioning system must also conform to the air
conditioning equipment manufacturer's recommendations.
Air Conditioning Ducts
Use separate computer room air conditioning ductwork. If it is not separate from the rest of the building, it
might be difficult to control cooling and air pressure levels. Ductwork seals are important for maintaining a
balanced air conditioning system and high static air pressure. Adequate cooling capacity means little if the
direction and rate of air flow cannot be controlled because of poor duct sealing. Also, the ducts should not be
exposed to warm air, or humidity levels may increase.
Humidity Level
Maintain recommended humidity level at 40 to 60% RH. High humidity causes galvanic actions to occur
between some dissimilar metals. This eventually causes a high resistance between connections, leading to
equipment failures. High humidity can also have an adverse affect on some magnetic tapes and paper media.
